.......fake fuses query......

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Hi,
I am on holiday, staying in my parents static caravan, and the hot water boiler stopped working overnight.
The boiler is a Heatrae Sadia Multipoint 50 litre which is wired to a fused switch on its own circuit. The boiler installation booklet says it should be wired to a 13 amp socket, which it is.
The fused switch socket has burnt out and I am wondering if someone has used a fake 13 amp fuse. The circuit breaker at the consumer unit hadn't tripped either, which concerns me as well.
I have attached some pictures and would be grateful for your feedback please.
 

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A real fuse is readily available and very cheap, not much point in making fakes. But there are a few idiots who will wrap a blown fuse in aluminium foil.

You had better turn off the power and fit a new S-FCU, should only cost a few pounds depending where you get it. Get one with an indicating neon or LED. Your old one has a flex outlet, presumably you need the same type. More modern ones often have the flex outlet concealed in the bottom edge, so look carefully. The Crabtree and MK brands may be better than cheaper ones.

https://www.screwfix.com/p/crabtree-1-gang-13a-dp-switched-fused-connection-unit-neon-white/53831

https://www.screwfix.com/p/mk-13a-dp-switched-fused-connection-unit-with-flex-outlet-white/13479

https://www.tlc-direct.co.uk/Products/BG951.html

Buy some spare fuses as well
https://www.wilko.com/en-uk/wilko-fuses-13amp-4pk/p/5349440


BTW, the thermostat should turn off the heater when the water is hot, and remove the load. Verify that your thermostat has not failed, leaving the heater running continuously. This can cause overflow of boiling water, or worse, which is dangerous and costly. Running correctly, the heater will take about 1 minute per litre of water in the device.

Photograph the consumer unit "fusebox" in the caravan,please. If the water heater has its own circuit breaker, you could use a different switch at the appliance.
 
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I would suspect a loose connection in the FCU - or loose fuse holder.
Try a new one and make sure all the wires are stripped back to undamaged wire.

This is unlikely to be caused by a fake fuse nor would such a fault cause a fuse to blow.
 
Richstar are believed to be counterfeit

This from https://www.pat-testing-training.net/articles/fake-fuses.php seems to confirm this belief.....

fuse-15.jpg


The fuses are branded as Richstar and have the ASTA and Kite marks. The end caps have a dull matt finish. These look to to be genuine. There is also an ASTA licence number:497 and a Kitemark number: KM34254. BEAB website and BSI Kitemark website both have a search facility to check the licence numbers. I couldn't find a matching licence on either site. I contacted BSI and they confirmed that the Kitemark number is not registered and the fuse should be considered as counterfeit.

The circuit breaker at the consumer unit hadn't tripped either, which concerns me as well.

The fuse wire was probably glowing red hot at less than 13 amps so the circuit breaker would not be overloaded even though the "fuse" was incinerating the fuse holder

 
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The fuse wire was probably glowing red hot at less than 13 amps so the circuit breaker would not be overloaded even though the "fuse" was incinerating the fuse holder

It is well known that 13A fuses, FCUs and plugs, for whatever reason (usually because something fits less than perfectly), do not like 3kW immersion heaters, although I have known some to last for years.

However, should the accessory (which the fuse is in) not be able to cope with an overload heating the fuse to an extent insufficient to cause it to rupture.
This does not mean this was an actual overload, only that it is suggested that the fuse must actually have been the equivalent of around 8 or 9A.

I would think a counterfeit 13A fuse would be a lot higher than 13A.
It seems a bit daft to manufacture counterfeit 13A fuses which contain fuse wire which is less than 13A. Why not call it whatever it is?


It being physically smaller is much more likely to cause a poor connection.
 
I would think a counterfeit 13A fuse would be a lot higher than 13A. It seems a bit daft to manufacture counterfeit 13A fuses which contain fuse wire which is less than 13A. Why not call it whatever it is?
Quite. I'm actually not quite sure what is fake in a 'fake fuse' but, as you imply, one might imagine that most fakes would be less likely to result in overheating of the FCU/plug/whatever in was installed in.

Kind Regards, John
 
In a genuine fuse the fuse wire is connected to the end caps in a way that reduces the amount of heat that can reach the end caps from the fuse wire. In many fakes the wire is in direct contact with the caps and the caps heat as the wire heats.

In fakes this means the end caps get hotter than they should and the wire is cooled. The amount of cooling depends on how heat conductive the fuse clip is. The more cooling the higher the rupture current so the fuse "rating" depends on the construction of the clips holding the fuse.

A genuine fuse is filled with silica sand to quench the arc that forms when the fuse blows. When a fake with little or no sand blows the very hot plasma arc can persist for a significant length of time. This can be until the fuse and its holder are cremated and the fuse and / or the holder fall apart.
 
Thanks for your comments.
I have installed a new 13 AMP FCU and the boiler is up and working. I will switch the boiler off when not needed.
My Dad will speak with an electrician to investigate further as this is the second time this has happened. I think what JohnD mentioned would be a good approach to a permanent solution as the boiler is on its own circuit.

Photograph the consumer unit "fusebox" in the caravan,please. If the water heater has its own circuit breaker, you could use a different switch at the appliance.
 
Yes, if it has a 16A MCB (or possibly higher depending on the cable used) then the FCU is not necessary.

A 20A switch is all that would be required.
 
Turn it on and watch if the thermostat turns it off automatically when hot. It should be within about 50 minutes if fully cold, much less if it is already warm or partly hot.

It will be quicker in summer, when the incoming water is not very cold, than in winter.
 
In a genuine fuse the fuse wire is connected to the end caps in a way that reduces the amount of heat that can reach the end caps from the fuse wire. In many fakes the wire is in direct contact with the caps and the caps heat as the wire heats.
I'm not sure what sort of arrangement you are talking about, but I've just taken apart a few 'reputable' (hopefully not fake) ones and (although I've failed to take photos which are particularly useful) the fuse wire appears to be simply welded/brazed/soldered onto a little dimple on the inside of the end of the cap, clearly in complete thermal contact with the cap.

Kind Regards, John
 
The German bottle fuses do have sand in them and the fuse-able link is a thin strip with holes in the centre so just the centre bit fuses, not the whole wire, there are also fuses with springs in them, however every BS 1362 I have smashed has had just a simple wire, no necking near centre to concentrate heat to centre.

However I don't know what the wire is made of? Some fuses have lead wire which ruptures at a lower temperature, we have all seen fast blow, and slow blow fuses, the the BS 1362 is rather basic.
13+amp+fuse.jpg

Even after 10 to the fourth seconds (around 24 hours) looking at between 22 and 35 amp to rupture them, they work well with a short circuit, but not so good with overload.

Even with an A1 BS1362 fuse you still get plugs over heating.
 
Annex 1
Information provided by Cooper Bussmann
With regard to identification of
counterfeit/copy fuses, Bussmann suggest the following,
The ceramic body is much ´whiter´ than the bodies used by approved manufacturers.
The body wall is also approximately twice the thickness of the wall of the approved fuses.
The colour of the print, which must be red for a 3A fuse, is more orange than the ink used by approved manufacturers.
The ASTA and BSI logos appear to be larger (longer) than those printed on approved fuses.
The ink used has a gloss finish compared to the matt finish of approved manufacturers.
The fuse cap base metal may be brass rather than copper.
In some counterfeit/copy fuses no eyelet is used in the internal construction and the wire often can be seen to be
trapped against the side wall of the tube under the cap causing a bulge. Often the wire protrudes beyond the edge of
the cap.
Where an eyelet is used to attach the fuse element to the end cap it is much deeper than eyelets used by approved
manufacturers and uses solder to make the connection. No solder is used in the end contact of the approved fuses.
The weight of the counterfeit/copy fuses is almost always below 2.3 grams, often as low as 1.7 grams. This is a clear
indication that the fuse is not filled with sand or does not have the correct amount of sand.
 

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